package offer;

public class offer25 {
}
class Solution25 {
    public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
    if(l1==null) return l2;
    if(l2 ==null) return l1;
    ListNode fakeHead = new ListNode(-1);
    fakeHead.next = l1;
    ListNode pre = fakeHead;
//    ListNode cur = l1;
    while (l1!=null&&l2!=null)
    {
        if(l1.val<l2.val)
        {
            pre.next= l1;
            pre = l1;
            l1 = l1.next;
        }else
        {
            pre.next = l2;
            pre = l2;
            l2 = l2.next;
        }
    }
    if(l1==null)
        pre.next = l2;
    if(l2==null)
        pre.next = l1;
        return fakeHead.next;
    }
}